building plugin – save image link to db to be called in group header

If I wanted to save a link to a image in the group meta, to be called and displayed in the group header, how should the form look ( I think I just save the link via value=”" in the form )?

Im using a checkbox so the group creator decides ( checks ) which ‘image/s’ they would like to be assosiated with.

Would I just save the link to the image, to the db? Also were would it be best to store the image, in the plugin folder under images or something?

// create the form to add the card
function gcard_add_card_form() {
<label for="group-card"><?php _e( 'Card desc', 'gcard' ) ?></label>
<input type="checkbox" name="group-card" id="group-card" value="" />

add_action( 'groups_custom_group_fields_editable', 'gcard_add_card_form' );

// Save the card value/s in the group meta - perhaps use serialize() and maybe_unserialize()
function gcard_save_card( $group_id ) {
global $bp;

$id = $bp->groups->new_group_id;
$id = $group_id;

if ( $_POST['group-card'] )
groups_update_groupmeta( $id, 'gcard_group_card', $_POST['group-card'] );